The water box of such a heat exchanger is generally molded as a single piece of plastic having at least one liquid inlet or outlet fitting. The free end of this fitting generally includes a rim projecting outwardly from its outside surface. The end of an elastically-deformable hose, e.g. made of rubber or analogous material, is thrust over the end fitting and its rim, and then serves to connect the end fitting to a liquid circuit. The end of the hose is clamped around the end of the inlet or outlet fitting by means of a conventional clamping collar which is disposed beyond the rim and around the end of the hose and the end fitting which it encloses so as to prevent the hose from being pulled off the fitting, for example by direct traction on the hose or by a sudden change in the pressure of the liquid flowing along the hose.
However, awkward problems are associated with molding such a rim on the outside surface of the free end of the inlet or outlet fitting. The mold which determines the outside shape of the end fitting and its rim is in two parts which meet along a join plane that passes through the axis of the fitting. As a result, on unmolding there is a risk of flash or at least a mold line running along the outside surface of the fitting in the join plane, and even quite a small mold line can give rise to leakage of liquid when the hose is mounted on the fitting and held in place by a clamping collar. It is therefore often necessary to remove the mold line after the water box and its inlet or outlet fitting have been unmolded, thereby increasing production costs. Further, the rim on the outside surface around the end of the inlet/outlet fitting requires the end of the hose to be put into place during assembly by force.
Preferred embodiments of the present invention avoid the above drawbacks.